The proposed research will test for a relation between the transition from groping to foresight and developmental change in the lateralization of action in infants' problem-solving. Six problem-solving tasks will be used in a cross-sectional study at 11, 14-1/2, and 18 months of age. Three tasks can readily be solved with one hand, for example, a barrier task where infants reach around a clear plexiglass partition to retrieve a toy, whereas three tasks require both hands, for example, a box task where infants must hold open the door of a box in order to remove a toy. Across trial each task will be scored for a groping or foresightful solution: For example, in the barrier task, a groping solution involves contacting the barrier with either hand before securing the toy, whereas a foresightful solution involves a unimanual detour reach without any prior barrier contact. Similarly, in the box task, a groping solution involves incomplete differentiation of roles for the two hands for opening the door and removing the toy (e.g., opening the door with both hands, and removing the toy with one hand), whereas a foresightful solution involves complete differentiation of roles for the two hands (i.e., opening the door with one hand, and removing the toy with the other hand). In addition, across trials, each task will be scored for handedness, the unimanual tasks for the retrieving hand with or without involvement by the other hand, and the bimanual tasks for the respective roles of the two hands (e.g., leading off the bimanual sequence with one hand and completing the sequence with the other hand). Based on past findings, one pattern of results is expected which will have considerable theoretical value in understanding the development of sensorimotor intelligence and hemispheric specialization. Specifically the emergence of right hand unimanual foresightful solutions in the unimanual tasks will coincide with the onset of a hand preference in foresightful solutions involving complete differentiation of roles for the two hands (right hand leading, left hand following) in the bimanual tasks. Such a developmental relation would implicate developmental change in hemispheric specialization for motoric control in the transition from groping to foresight and would suggest left hemisphere control over the left as well as the right hand. This view is consistent with other evidence for the role of the left hemisphere in the planning/or organization of action.